The present invention generally relates to an angularly adjustable releasably lockable joint mechanism for rigidly joining first and second parts at a selected orientation, and more particularly to an angularly adjustable releasably lockable joint mechanism having a plurality of patterned protuberances forming concavities so that a tip of actuator can engage and disengage therefrom.
Such a joint mechanism is disclosed for example in U.S. Pat. No. 5,280,871. A movable rod has a ball fixed at its bottom, and the ball is provided with a plurality of holes orderly and equally spaced apart in the surface for the functional end of a locating pin of a supporter to selectably engage one of them to keep the movable rod secured in an angle needed. Such a dimpled ball and an actuator having a spherical tip are also shown in U.S. Pat. No. 3,433,510. U.S. Pat. Nos. 3,841,769 and 4,620,813 show a socket having protuberances and a ball having dimples or indentations which engage to fix the orientation of the arms attached thereto. U.S. Pat. No. 3,691,788 shows a ball having a grooved surface and an actuator having a spherical tip which locks up by engaging a groove. U.S. Pat. No. 892,105 shows a ball and socket whose surfaces are both knurled.
Angularly adjustable, releasably lockable ball joints are commonly used as part of an umbrella assembly, to hold a suspended canopy locked at an angle to horizontal. Assemblies of this type are shown in U.S. Pat. Nos. 4,674,523 and 5,002,081. In general, these prior art ball joints involve:
a ball attached to a shank forming part of the suspension stand;
an actuator or screw spindle carrying the canopy;
a housing engaging the ball and spindle so that they cannot separate, but which is operative to enable the spindle to be angularly adjusted when the actuator is disengaged; and
a concave socket or pin at the end of the spindle, for frictionally engaging the ball to lock the spindle and ball together and fix the canopy at a desired angle.
The frictional engagement of ball and socket as well as a dimpled ball and spherical pin actuator have been found to be insufficient when subjected to high torsional forces.
One objective of the invention is therefore to modify the joint mechanism described above to provide a stronger locking action between the actuator and the rounded member.
In combination with the features of the joint mechanism described above, the invention is characterized in that
the rounded member having a plurality of patterns of spaced-apart protuberances covering at least part of its surface, the protuberances of each pattern forming a concavity therebetween;
the patterns, and protuberances being mainly consistent in shape, area and size, the effective patterns having a regular polygonal configuration;
the protuberances, actuator tip and pattern being dimensioned so that the tip can penetrate the concavity of each pattern and simultaneously contacts all of the protuberances of the pattern that it penetrates but remains spaced from the bottom of the concavity at full penetration, whereby the tip and pattern of protuberances lock together.
The invention has the following advantages:
the locking capability is greater than one obtains with a dimpled ball;
by arranging the patterns in accordance with a geometric design, the longitude and latitude of the concavity sites is predictable;
the use of the triangular pattern yields a large number of concavity sites in the case of a rounded member that is spherical and of given diameter. Compared to an equivalent pattern of dimples, twice as many concavity sites result simply through the formation of the protuberances in place of the dimples; and
it is possible to address and achieve locking at each individual position by electronic means, since all of the concavity sites or locking positions are mathematically definable.
The rounded member may be spherical and could be defined by a ball.
The invention refers to an angularly adjustable, releasably lockable joint mechanism for rigidly joining first and second parts at a selected orientation, said mechanism comprising a rounded member having a plurality of concavities on its surface and being secured to the first part, a disengageable actuator having at least one tip and being operative to advance the tip to lock up with the rounded member by penetrating at least one concavity or to retract the tip to disengage it from the rounded member, said actuator being connected with the second part, and means for holding the parts, rounded member and actuator together, said means being operative to allow the parts to change relative orientation when the actuator tip is retracted.
This mechanism is particularly adapted for use with angularly adjustable, locking devices subject to high torsional forces.
The invention comprises patterns of three and four protuberances as well as any polygons of more than four protuberances. But complete locking could also be achieved between just two protuberances and one actuator: In this case the rounded member is defined by two smooth semi-spherical halves joined in the middle by a narrow sometimes recessed surface in the middle. This recessed surface is fitted with continuous half round protuberances extending between the semi-spherical halves along its surface and the whole unit is contained in a suitable shell structure. Here it would take only two protuberances and one incoming suitable actuator to ensure locking. The same would also apply to a gear-like structure contained in a suitable shell and locked by an actuator.
According to the invention, the penetrating tip of the actuator contacts the surfaces of the protuberances defining the penetrated concavity, but does not contact the surface of the rounded member defining the bottom of the concavity. But after extended use, the protuberances may show significant wear, allowing the actuator tip to touch said surface, To prevent such an incomplete locking, it may be useful to add a depression into the surface of the rounded member at each locking site which would in conjunction with the protuberances result in a kind of sine wave surface. This could prolong the use of the joint mechanism before the actuator tip touches the bottom of the concavity.
The configuration of protuberances preferably form triangular or square patterns, or the protuberances could define a combination of square and triangular patterns on said rounded member.
The actuator may have multiple tips disposed to penetrate simultaneously more than one concavity. Furthermore, the actuator or its head defined by the tip may have a floating seating to enable self-adjustment.
In a preferred version, the actuator can be biased, such as by spring loading, such that the actuator tip is prevented from falling out of contact with the protuberance or cluster of protuberances, when the actuator is not in the locking position.
It is also within the invention to use an actuator, the configuration of this actuator being similar to that of the rounded member including the protuberances.
The joint mechanism according to the invention will find application in different fields, for example in the field of prosthetics (defining an orthotic or prosthetic joint), wheel-chairs (head rest joint) and for example in connection with a sunshade umbrella.